Geologic controls on hydraulic conductivity in a karst-influenced carbonate bedrock groundwater system in southern Ontario, Canada

Abstract

A large set of hydraulic conductivity values has been integrated with the geologic characterization of a Paleozoic-age carbonate groundwater system to assess the relative influence of specific geologic features on hydraulic conductivity. Three geologic controls are investigated: (1) proximity to bedrock valleys within a regional stress field; (2) carbonate rock texture; and (3) sequence stratigraphic breaks. Results demonstrate that high hydraulic conductivity values do not correlate with a single geological feature, but are associated with various features that have been enhanced by carbonate dissolution. Predicting the spatial distribution of hydraulic conductivity in carbonate rocks requires a regional understanding of the geological history with a conceptualization of where and when waters have interacted with the rocks to dissolve and enhance porosity through geologic time. This investigation focused on a region in southern Ontario, Canada, and concludes with a map identifying the area with the greatest probability of encountering high hydraulic conductivities in the main hydrostratigraphic unit, the Gasport Formation. The map supports the selection of groundwater resource exploration targets for a local municipality. Beyond the local benefits of this work, this investigation offers an approach that can be adopted by practitioners exploring for bedrock groundwater resources or characterizing contaminant transport pathways in complex karst-influenced, carbonate bedrock groundwater systems.